Raid devices created on partitions would most likely be software raid as I
am
not sure if you should create partitions on a software raid device,
although
linux would probably let you.. The technology is mature and sound, and the
processor load is not that great.
Partitions on top of raid devices would most likely be hardware raid. Some
devices are better than others, not just the hardware, but the driver
support.
You can not answer your question that easily, though. The "type" of raid
device you create is what will tell you how recoverable it is. A stripe or
raid 0 is not resilient at all. The loss of one drive will destroy your
data.
How much you can recover would depend on the size of the stripes and the
size
of the data. A mirror or raid 1 is infinitely more recoverable, because a
complete copy of the data is on each drive.
Raid 5 or better has a somewhat less chance of survival, but is better
than
raid 0 chance of surviving.
None of them would be reliable enough to use without some sort of backup.
Data security shouldn't depend on the type of or lack of raid. Data is
secured
by limiting access.
The better performing raid types aren't always the best for survivability.
Yes, I know all of that...
Either you didn't understand my question or I didn't express myself well (I
admit to the latter).
What I meant was: the same type of RAID considered, which situation would
have been proved better:
- RAID devices created on top of partitions or partitions created on top of
RAID devices. (I am, of course, talking about Linux software RAID).
And that under the three aspects of performance (CPU utilization, disk
transfer rate, etc), data security and ability to recover from a disk crash.
The mdadm device, the kernel and the hardware relate to each other in ways
that *may* make a difference according to the relative order in which the
partitions and RAID devices are created. (I am assuming EXT3 partitions
here.) I thought that someone here might have made that experience and would
be able to tell me, tell us, something about it.
Thank you!
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